This application is a divisional of application Ser. No. 12/681,182, which is the National Stage of International Application No. PCT/JP2008/002676, filed Sep. 26, 2008 and also claims the priority of Japanese Patent Application No. 2007-257302 filed on Oct. 1, 2007 in Japan and Japanese Patent Application No. 2008-113564 filed on Apr. 24, 2008 in Japan, and the contents of which are incorporated herein by references.
1. Technical Field
The present invention relates to a duplexer used in a mobile phone and the like.
2. Background Art
As shown in FIG. 14, conventionally, this kind of duplexer includes an acoustic wave element 1 having an antenna terminal 1A, a reception terminal 1B, and a transmission terminal (not shown), and a ceramic substrate 2 on which the acoustic wave element 1 is set. The substrate 2 internally has a columnar conductor 2A electrically connected to the antenna terminal 1A and drawn to a back surface of the substrate 2, a columnar conductor 2B electrically connected to the reception terminal 1B and drawn to the back surface of the substrate 2, and a columnar conductor (not shown) electrically connected to the transmission terminal (not shown) and drawn to the back surface of the substrate 2. Since a ground pattern is not provided between the drawn part of the columnar conductor 2A and the drawn part of the columnar conductor 2B on the back surface of the substrate 2, a solder and the like prevents a short circuit from generating between the drawn part of the columnar conductor 2A and the drawn part of the columnar conductor 2B.
In addition, Japanese Patent Laid-open Publication No. 2000-49565 is known as a conventional art document information relating to this application.